Hermetically sealed heaters



Dec. 13, 1960 L. E. NORDHOLT ET AL 2,964,034

HERMEITICALLY SEALED HEATERS Filed Dec. 51, 1956 6 Sheets-Sheet 1 Fig.4.

Dec. 13, 1960 E. NORDHOLT ETAL 2,964,034

HERMETICALLY SEALED HEATERS 6 Sheets-Sheet 5 Filed Dec. 31. 1956 FIG.15.

nyvENToRs LOUIS E.-NORDHOLT RICHARD M. SCHERER ATTORNEYS FIG. 14.

Dec. '13, 1960 E. NORDHOLT ET AL 2,964,034

HERMEITICALLY SEALED HEATERS 6 Sheets-Sheet 4 Filed Dec. 31, 1956 LOUISE. NORDHOLT RICHAR D M. SCHE R ER Wfiflb Mm ATTORNEYS Dec. 13, 1960 L.E. NORDHOLT ET AL 2,964,034

- HERMETICALLY SEALED HEATERS Filed Dec. 31, 1956 6 Sheets-Sheet 5 FIG.1].

INVENTORS LOUIS E.NORDHOLT RICHARD M. SCHERER ATTORNEYS L. E. NORDHOLTET AL HERMETICALLY SEALED HEATERS Dec. 13, 1960 6 Sheets-Sheet 6 FiledDec. 31. 1956 INVENTORS LOUIS E. N ORDHOLT R I CHA RD M. S OH E R E R WATTORNEYS United States Fatent O The present invention relates toheaters and particularly to gaseous fuel burning space heaters having acombustion system hermetically sealed with respect to the space or roomto be heated.

So-called hermetically sealed heaters are characterized by a combustionsystem communicating with the exterior of the building only and beingisolated from .the air in the room to be heated. Su'ch heaters havenumerous advantages over other types of heaters, such as: assuring nocontamination of the air in the room by combustion products; using onlyoutside air for combus- '.tion purposes; and preventing the escape erany gaseous fuel into the room, should combustion be accidentally 'orinadvertently terminated while the fuel flow continues. Due to thenature of 'the combustion system of these rheaters', it has been foundto be highly desirable, if not necessary from 'a practical "standpoint,to mount them "on the inside -of an'eX'ter-nal building wall so that theoutside -venting system for the combustion chamber may be iarianged inclose proximity'to the combustion chamber itself. In this regard, theproximity of the combustion chamber to the building wallhas in somecases presented serious fire hazards as well as construction or mountingproblems.

A further disadvantage of sealed heaters is that slight changes inexternal wind velocity and conditions are readily transmitted directlyto the combustion chamber through either the combustion air inlet or thecombus- 'tion products outlet of the venting system, so that unless thecombustion air inlet and combustion products outlet are provided withmeans compensating for such wind changes, an undesirable pressureunbalance may 'be created in the combustion system tending to impairheater operation and in some cases blowing out the flame at the burner.

It is a principal object of the invention to provide a novelwall-mounted, hermetically sealed heater overcoming the foregoing aswell as other disadvantages of prior art sealed heaters.

A more specific object resides in the provision of a novel cabinet andwall mounting structure for sealed heaters particularly useful forpreventing overheating of the cabinet and the building wall on which theheater is mounted.

Another object is to provide a hermetically sealed heater including anovel arrangement of natural and forced convection air passageways forcirculation of room air whereby heated room air will be simultaneouslyand advantageously discharged from the heater adjacent the door level ofthe room and also at a level disposed thereabove.

An additional object is to provide a novel wall mounting structure forsealed heaters facilitating the installation of such heaters adjacent anexterior building wall and obviating the necessity of making anypreliminary expensive or time-consuming alterations to the wall.

Yet another object is to provide an external venting Patented Dec. 13,1960 2 means for concentric combustion air inlet and exhaust gasconduits associated with a sealed combustion chamber insuring proper anddesired flow through the combustion system.

Further objects and advantages of the invention will be in .part obviousand in part pointed out hereinafter.

The novel features ofthe invention may best be made clear from thefollowingdescription and accompanying drawings in which:

Figure l is a top plan view of a-heater of the invention shownattachedto a building wall, the latterbeing in horizontal section;

Figure 2 is a front elevational view of the heater in Figure 1 with thebuilding wall shown fragmenta-rily;

Figure 3 is a side elevational view of the heater of Figure 1 with thebuilding wall shown in vertical section;

Figure-4 is an enlarged elevational view 'of the outside venting meansfor the heater of Figure 1; I

Figure 5 is an enlarged side elevational view of the heater of Figure 1,with certain parts thereof broken away and other .parts in section;

Figure 6 'is an enlarged fragmentary sectional view taken along line 6-6of Figure 1;

Figure 7 is an enlarged sectional view taken along line 77 of Figure 1;

Figure 8 is an enlarged, fragmentary, horizontal, sectional view takengenerally along line 88 of Figure 2;

Figure 9 is an enlarged sectional 'view of certain parts 'of the heatertaken along line 99 of Figure 2;

Figure 10 is-a front elevational view of the parts shown in Figure9,with some of them broken away and others in section;

Figure 11 is 'a front elevational view 'of the parts of Figure 9 on aslightly reduced scale and partially cut away;

Figure 12 is an enlarged fragmentary front elevational view of apreferred embodiment ofthe burner structure of the invention, andshowing an exemplary form-0f mounting means for the burner;

Figure 13 is an end elevational view of the burner of Figure 12; I

Figure 14 is an enlarged sectional view taken along line 1414 of Figure12;

Figure 15 is an enlarged sectional view taken along line 15-15 of Figure12;

Figure 16 is a vertical sectional view corresponding to Figure 14 butillustrating a modification of this part of the burner;

Figure 17 is a front elevational view of a preferred form of mountingbox for the heater;

Figure 18 is a side elevational view 'of the mounting box of Figure 17;

Figure 19 is a top plan view of the mounting box of Figure 17 partiallybroken away and in section;

Figure 20 is a fragmentary rear elevational view 'of the mounting box ofFigure 17, partially broken away; and

Figure 21 is an enlarged, fragmentary, side elevational view of apreferred form of forced air circulating means for the heater.

Referring now to the drawings, a heater'20 embodying the invention(Figures 1, 3, 5) is adapted to be mounted against a building wall 22above the floor 24 of the room to be heated. The heater 20 preferablyincludes an internal combustion heating unit 26 (Figure 5) hermeticallysealed from the room in which the heater is arranged and including aventing structure extending through a hole 28 in the wall 22 to theexterior of the building for establishing communication between thecombustion chamber and the outside atmosphere.

The heater 20 includes a mounting box 'or combination mounting andshielding structure 30 (Figure 5.) adapted 3, to be attached to theinner surface of the building wall 22 to receive the heating unit 26. Acabinet or outer decorative shell 32 encloses the heating unit 26 and isprovided with suitable openings for the circulation of room air throughthe heater.

The mounting box 30, as best seen in Figures 5, 8, and 17 to 20,preferably includes back 34, side 36, bottom 38, and inclined top 40walls. The back wall 34 is formed with an upper aperture 42 therein foralignment with the building wall hole 28. The side walls 36 preferablyextend a greater distance forwardly from the back wall 34 than thebottom 38 and top 40 walls and the upper ends of these side walls arebent in slightly. The top wall 40 preferably inclines upwardly andforwardly from the back wall 34 to the top of the side walls 36. A pairof vertically extending channel-shaped brackets 44 preferably areutilized for attaching the mounting box 30 to the building wall. Thesebrackets 44 are laterally spaced so as to be adjacent each end of themounting box and may be welded thereto. Brackets 44 may be secured tothe building wall 22 by suitable fasteners such as screws 46 extendingthrough holes provided at the upper and lower ends thereof into the wallwhereby the back wall 34 will be in spaced, parallel relation to wall22. A vertical notch or cut-out 48 is provided at the rear upper end ofeach bracket 44 for a purpose to be set forth hereinbelow.

The heating unit 26 (Figures 5, 8, and 9) preferably includes a hollowcombined combustion chamber and heat exchanger 50 and an air box orplenum chamber 52 rearwardly spaced therefrom and generally parallelthereto. A burner 54 is arranged in the lower part of the heat exchanger50 which defines the combustion chamber. The combustion chamberpreferably communicates with the air box through laterally spaced clucts56 and the air box and heat exchanger communicate with the atmospherethrough concentric conduits 58, 60 adapted to extend through aperture 42in mounting box 34 and be disposed within the hole 28 of the buildingwall.

The heat exchanger 50 may be constructed of mated front 62 and rear 64portions suitably connected as by welding of the peripheral flanges 66thereon and the combustion chamber portion thereof preferably is ofgenerally rectangular box-like configuration. An elongated horizontalopening 68 (Figure 11) is formed in the lower portion of the frontsection 62 through which the burner 54 may be inserted or removed, andthis opening is surrounded by a ridge 70 (Figure 9) cooperating with acomplementarily shaped perimetrical groove 72 on a cover plate 74 forclosing this opening. This cover plate 74 may be conveniently secured tothe heat exchanger 50 by means of spaced, vertical channel strips 76attached thereto and fastened as by metal screws (not shown) tocooperating-pairs of upper and lower brackets 78 on the heat exchanger.A sealing strip or gasket may be provided in the cover plate groove 72for sealing engagement with the ridge 70.

The central portion of the mating sections 62, 64 of the heat exchangerpreferably converge inwardly and upwardly from the combustion chamber(Figure and are inwardly deformed or grooved throughout a fiat V-shapedoutline at 80 adjacent their upper ends for contact with each other topresent a battle surface diverging upwardly and laterally (Figures and11) within the heat ex- -changer below the upper end thereof. Thegrooves defining this baffle surface terminate laterally inwardly of theside walls of the heat exchanger, and upwardly extending passageways 82are formed adjacent each side of the heat exchanger. The upper ends ofthe heat exchanger sections 62, 64 define a chamber communicating withthese passageways 82, and the rear section 64 is provided with centralaperture 84 above the groove 80 -therein for escape of the combustionproducts from the .heat exchanger.

The air box52 may be formed of convex mating sections 86, 88 joinedtogether as by welding of peripheral flanges 89. The front section 86 isformed with an upper aperture therein aligned with the aperture 84 inthe heat exchanger and the rear section 88 also is formed with anaperture therein, preferably coaxial with the aperture in section 86 butof a larger diameter. A conduit 90 is suitably mounted in the aperture84 of the heat exchanger and extends through the aligned upper aperturesof the air box for engagement to a collar-type fitting 92 connected tothe inner concentric conduit 58 (as best seen in Figure 5). The innerend of outer concentric conduit 60 is sealingly engaged to a collarfitting 94 which in turn is attached to the rear section 88 of the airbox in surrounding relationship to the upper aperture therein and alsobeing fitting in the upper aperture 42 in the mounting box 30. Suitablestructure is provided for attaching the air box 52 to the mounting box.Such structure may include upper and lower pairs of spaced brackets 96attached to mounting box rear wall 34 (Figures 5 and 17) and to whichthe upper and lower portion of the air box peripheral flange 89 may befastened by screws 97 whereby the air box will be in spaced, parallelrelation to the rear wall 34 while the vertical portions of the heatexchanger flange 66 are disposed adjacent the outer edges of themounting box side walls 36 (Figures 8, 9).

A radiation shield 98 preferably is arranged intermediate the air box 52and heat exchanger 50 as by attachment to the air box flange 89 throughspacers 100 (Figures 8 and 9) welded to such flange and also to asimilarly positioned flange on the shield 98.

The hole 28 in the building wall preferably is protected by a wall sealarrangement (Figures 5 and 8) including a circular tube 102 disposedtherein. The tube 102 preferably has an inturned lateral flange 104 atits inner end to which a plate 106 may be attached, the plate 106 beingfastened to the inside of the building wall 22 by suitable fasteners(not shown). Longitudinally extending spacers 108 of L-shapedcross-sectional configuration may be provided at spaced intervals aboutthe circumference of the tube 102 for engagement with the surfacedefining hole 28. Tube 102 encloses the concentric conduits 58, 60 andis radially spaced from outer conduit 60 while being of an axial lengthapproximately equal to the thickness of the building wall. The spacedefined between the tube 102 and outer concentric conduit 60 opens atits inner end into the space defined between the inner surface of wall22 and the back wall 34 of the mounting box.

The annular space between the concentric conduits 58, 60 will be seen tocommunicate at its outer end with the atmosphere and its inner end withthe air box 52, lower ducts 56, and combustion chamber, while the innerconduit 58 communicates at its outer end with the atmosphere and at itsinner end with the upper end of the heat exchanger through theassociated fitting 92 and duct 90. The outer conduit 60 preferablyterminates at the outer face of wall 22, whereas the inner conduit 58extends outwardly of wall 22. As will be evident, the combustionsupporting air will flow in the annular space between these concentricconduits to the air box and thence into the combustion chamber, whilethe combustion products or flue gases will flow through the innerconcentric conduit 58 from the upper end of heat exchanger 50 to theatmosphere.

Variations in external wind velo-citieshave caused serious diflicultiesin conventional sealed heaters by impair ing flow in the combustionsystem, and in some cases even extinguishing the burner flame. Theinvention contemplates the provision of novel venting structure at theouter ends of the concentric ducts 58, 60 for eifecting desiredcombustion characteristics at all times during heater operation,irrespective of external wind conditions. A preferred embodiment of thisventing structure 110 for the combustion system includes a directionalbaffle arrangement 112 for the inner conduit. 58 and an aperturedtubular sleeve 114 for the outer conduit 60 and defining the inlet forcombustion air. The tubular sleeve outer concentric conduits.

ages-ana 114 preferably is in the form of a screen or-other'p'erforatedstructure and is fitted at its inner end into an annular flange 116inturned from a mounting plate 118. This plate 118 is adapted to besuitably connected to the outer surface of wall 22 as by screws or nailswith its inturned flange 116 secured within the outer end of outerconcentric conduit 60. An annular groove 120 may be formed adjacent theouter periphery of plate 118 for the reception of caulking material or asealing ring engageable with the building wall.

The directional baifle arrangement 112, as best seen in Figures and 6,preferably includes an inner, dishshaped member 122 having a centralinturned flange 124 fitted within the outer end of the inner concentricconduit 58 and also includes an outwardly and rearwardly flaring convexsurface extending from the flange 124 to a vertical peripheral lip 126.The tubular sleeve 114 is in spaced enclosing relationship to the outerend of inner conduit 58, extending to a point adjacent the dish-shapedmember 122 and is fitted in an ou-tturned flange 128 of a circular plate130 connected to the peripheral lip 126 of the dish-shaped member, as bybolts 127 (see Figure 8).

Afiysuitable sealing and cementing material 132 may be applied in theV-shaped peripheral area defined between the dish-shaped member 122 andthe outer end of inner conduit '58. A closure cap 134 is arrangedoutwardly of the dish-shaped member 122 and including an imperforateflat central portion and an outwardly and a rearwardly flaring surfaceparallel to the corresponding surface of member 122 and also terminatingin a fiat peripheral lip 136. A plurality of baffles 138, 140 arearranged intermediate the cap 134 and member 122. Each of theseintermediate baffles includes a central aperture 142 aligned with theoutlet of inner conduit 58, and a r'earwa'rdly flaring surfacecomplementary to the corresponding surfaces of the cap 134 and member122 and also terminating in a similar corresponding peripheral lip 144.The intermediate bafiles and the closure cap may be secured in spacedrelationship to dish-shaped member 122 as by means of tubular spacerelements 146 encircling coaxial apertures in the peripheral lips ofthese members and rivets 148 inserted through these spacers and theperipheral lips as seen in Figure 6. Such a connecting structure may bedisposed at any desired number of points along the circumference of thealigned peripheral lips for providing a desired strong connection.

Intermediate baffles 138, 140 define with the closure cap 134 anddish-shaped member 122 as well as with each other, generally radiallyextending passageways of uniform width for discharge of the products ofcombustion from the inner concentric conduit 58 to the atmosphere in agenerally radial direction. Any gusts of wind flowing in a directionnormal to and toward the baflie arrangement 112 would be positivelyprevented from entering the heat exchanger either through the inner orExternal air for combustion supporting purposes will pass through thetubular sleeve 114 in a radial direction only inasmuch as the spacedplates 118, 130 define a radially extending inlet passageway therefor,this passageway being of uniform width. The air inlet at the tubularsleeve 114, therefore, as well as the combustion products outlet at theouter end of conduit 58 will be seen to be fully protected from any windcurrents flowing axially toward conduits 58, 60. If desired, althoughnot necessary, the lip 126 on member 122 may be extended radiallyoutwardly.

It will be appreciated that irrespective of the direction of externalwind flow, the directional bafiie arrangement 112 will effect anaspiration of the combustion products through the inner concentricconduit 58 for facilitating the desired directional flow through thecombustion system. This novel venting structure for the heater has beenfound to be highly satisfactory in establishing and maintaining desiredcombustion characterd istics notwithstanding severe changes inextc'rnalwind conditions. r

The burner 54 preferably is constructed with an elongated burner head150 (Figures 10 and 12) having the usual longitudinally spacedtransverse flame slots v152 therein and including an integral, generallyhorizontal tubular stem portion 154 communicating at one end with thecentral portion of head 150 through a slotted inner passageway 156(Figure 15 The tubular stern 154 includes a Venturi section 158 disposedadjacent the outer free end thereof, the latter end being enlarged andincluding a 'cut out area 160 defining a primary air inlet. A gasmanifold pipe fitting 162 is arranged in an aperture in a web 164 at theenlarged end in the tubular stem and is adapted to discharge gaseousfuel thereinto. This fitting 162 may be in the form of an elbow jointhaving a base 163 attached to the bottom of heat exchanger 50 (Figures10 and 13) for communication with a gas manifold pipe (not shown)extending through a suitable aperture in the heat exchanger bottom wall.The flow of fuel through the Venturi section 158 will increase theamount of primary air normally induced to flow into the stem 154 throughthe inlet 160 by reason of the flow of fuel at the inlet. A primaryfuel-air mixing will thus take place before the fuel discharges from theburner. In some instances, it is desirable to vary or adjust thefuel-air ratio within the burner 54. To facilitate such adjustment, agenerally radially outwardly extending lug 166 is formed adjacent theVenturi section 158 (Figure 14). This lug 166 is provided with alongitudinally extending tapped bore opening into the Venturi throat andinto which a screw 168 may be threaded. The outer end of screw 168 hasthe usual groove or kerf-17t) therein, While the inner end is formedwith a conical tip172. Rotation of this screw by an appropriate toolwill be effective to variably project the inner end 172 thereof withinthe throat of the Venturi, thereby offering greater or lesser resistanceto flow through the stem 154. Such variable flow resistance operates tovary the amount of primary air induced into the stem 154 in proportiontothe amount of gas flowing therein whereby the fuel-air ratio will becorrespondingly varied.

A lug 174 preferably is arranged at the left end of the burner head 150(as viewed in Figures 9 and 10) for engagement toa bracket 176 attachedto the innersurface of the left side wall of heat exchanger-50.- Thislug and bracket arrangement cooperates with the fitting 162 to supportthe burner within the heat exchanger (Figures 9, 10, and 12). Lug 174preferably extends outwardly and then downwardly from the burner headand is integral therewith, while the bracket 176 is hollow and slottedto receive the lug whereby the burner may be conveniently mounted indesired position in the heat exchanger by engaging the lug to thebracket and by engaging the Web 164 of stem 154 to the fitting 162. Thecoverplate 74 for the heat exchanger opening '68 may be formed with asuitable aperture (not shown) adapted to be aligned with the outer endof burner adjusting screw 168 for insertion of the adjusting tool. Thisaperture in the cover plate may be hermetically sealed by a removableplug or the like (not shown).

If desired, lug 166 on the burner tubular stern 154 may be formed toextend radially downwardly from the Venturi section rather thanupwardly, as lug 178 in Figure 1'6, and a pin 180 may be slidablyarranged in this lug. Pin 180 also includes a conical inner end182 andan outer head 184 biased by leaf spring 186 against an adjusting screw188, the latter screw being threadedly engaged to nut 190 and extendingthrough the bottom of the heat exchanger front section 62 for convenientexternal adjustment.

The gas manifold pipe connected to fitting 162 communicates with and isconnected to the usual gas supply conduits and room thermostaticcontrols (not shown) for automatic control of fuel flow. A pilot burnerQr other suitable main burner ignition device may be convenientlyarranged within the heat exchanger 50 adjacent the burner head 150. Asseen in Figure 10, a conventional pilot burner 192 and thermocouple 193arrangement may be attached to and extend through a horizontal ledge 194formed by recessing the lower front portion of the heat exchanger at196.

The heat exchanger cover plate 74- preferably is formed with atransparent disc 198 of suitable heat-resisting material for externalvisual observation of the pilot burner flame. This disc 198 may be inthe form of a cap removably fitted to cover an opening in the coverplate 7 4 whereby an igniting means may be inserted therethrough forlighting the pilot burner.

The vertical portions of the heat exchanger peripheral flange 66cooperate with the adjacent outer edges of the mounting box side walls36 to define a space opened at the upper and lower ends thereof forcirculation of room air in heat exchange relationship with the variousparts of the heating unit in this space, namely the rear section of theheat exchanger, the radiation shield 98 and the air box 52. A means foreffecting a forced downward circulation of air through this space may beprovided, whereby heated air will be discharged adjacent the floor 24 ofthe room to be heated. For this purpose, an angulated fitting 200(Figures 8, 9, and 17) preferably is arranged in the left corner ofmounting box 30 and is attached to the back wall 34 and left side wall36 thereof, functioning with these latter walls as an upwardly extendingduct. The right side wall 202 of the angulated fitting 200 extendsdownwardly beyond the front wall 204 thereof to the bottom wall 38 ofthe mounting box and defines a lower opening for the duct, which is alsoopened at its upper end, the latter preferably being disposed adjacentthe horizontal central line of the mounting box.

An apertured plate 206 (Figures 18, 19) is arranged adjacent the lowerportion of the side wall 202 and may be suitably connected in verticalposition thereto as by welding. This plate 206 extends perpendicularlyoutwardly from the mounting box back wall 34- to a position forward ofthe outer edges of the side walls 36 and preferably is reversely bentforwardly at its back edge for receiving the inner or back edge of asimilarly apertured plate 208 similarly arranged and suitably connectedto a blower housing 210. A conventional horizontal axis, impeller-typeblower (not shown) is journaled in the housing 210 and receives powerfrom a suitable source such as prime mover 212. An upper tangentialoutlet duct 214 extends from the blower housing while the left blowerhousing side wall (Figures 10 and 11) is formed with an inlet openingaligned with the apertures in the plates 206, 208 constituting the axialinlet for the blower. The lower opening in the fitting 200, as well asthe apertures in plates 206, 208 and the blower inlet may be enclosed bya fitting 216. This fitting 216 is suitably connected to the adjacentfitting 200, plate 206, and the mounting box and may be formed with anouter surface flaring horizontally outwardly from the left side wall 36of the mounting box. Thus, the blower inlet will be in communicationwith the space in the heater through the opened upper end of fitting200.

After the mounting box and heating unit have been installed in desiredposition adjacent the building wall 22, the cabinet 32 is fitted overthese parts. The cabinet 32 preferably includes interconnected side 218,top 220, and bottom 224 pieces (Figures 1 to 3, 5 and 8) of sheet metalconstruction. The rear edges of the side pieces 218 preferably areturned inwardly for desirable engagement.

with the building wall 22 while the front edges thereof may be turnedinwardly and rearwardly for facilitating attachment to the side walls226 of the top piece 220. The top piece 220 extends from the top of thecabinet downwardly to a position intermediate the height thereof and theupper part of this piece is conveniently attached to.

the upper ends of the side pieces 218. Top'piece 2 20 terminates in adownwardly turned lip or flange 228 at its extreme rear upper end. Thisdownturned lip 228 is conveniently disposed in the notches 48 at theupper ends of the channel brackets 44 attached to the mounting box. Byreason of this arrangement, attachment and removal of the cabinet 32 isgreatly facilitated. However, additional supporting means for retainingthe cabinet in position may be provided.

The bottom cabinet piece 224 may be formed with an tip-turned lip 230 atits rear end for engagement with the building wall and is convenientlyattached to the bottom of the side pieces 218. The cabinet furtherincludes lower front piece 232 attached to the bottom piece and engagingthe top and side pieces to completely enclose the space within theheater. The top 220 and lower 232 pieces preferably extend in generallyconverging directions from the upper and lower ends of the cabinetrespectively to define a forward disposed space or passageway in theheater for the passage of room air to be heated. These pieces 220, 232are provided with suitable grilles constituting room air inlets andoutlets for the heater. These grille openings are indicated by numeral234 for the lower front piece 232, while the top piece 220 preferably'isformed with a relatively large central opening therein in which a curvedperforated member or grille 236 may be disposed. The upper end of toppiece 220 may be provided with additional openings 238 communicatingwith the space defined between the mounting box back wall 34' and thebuilding wall, or the member 236 may be constructed and arranged toextend to this part of the top piece and communicate with said space.

The lower front piece 232 may be suitably hinged at its bottom to thefront edge of the bottom piece 224 and retained in closed position byengagement of a spring latch detent 240 with the bottom of top piece220. Manually operable controls (not shown) may be arranged within thelower part of the heater, and access will be afforded to them throughthe hinged front piece 232. An outer hand grip portion 242 (Figures 2and 5) may be provided at the upper end of front piece 232, protected bya heat shield 244.

To furnish additional support for the cabinet 32, inwardly extendinghorizontal brackets 246 may be attached to the side pieces 218 (Figure8) for convenient connection as by screws (not shown) to the heatexchanger peripheral flange 66. Also, the upper end of the cabinet toppiece 220 may be constructed and arranged so that it rests on the top ofthe mounting box 30 when the former is fitted over the heating unit.

It should be noted that the cabinet side pieces 218 are spaced outwardlyfrom the parallel side walls 36 of the mounting box, whereby an airjacket for the side and rear of the heating unit is provided. Thisjacket communicates with the lower portion of the heater since themounting box side and rear walls terminate above the bottom cabinetpiece, the latter preferably being disposed above the room floor 24.

Operation of the heater will now be described. Fuel will flow to themain burner, for ignition by the pilot burner, in response to a demandfor heat in theroom or zone to be heated sensed by the thermostaticcontrol means positioned therein. Combustion of the fuel in the heatexchanger 50 will produce an upward flow of combustion products throughthe heat exchanger and inner conduit 58 to be discharged to atmospherethrough the baffie arrangement 112. This how of combustion gases willinduce an inward flow of external combustionsupporting air into thecombustion chamber through the inlet sleeve 114, the annular spacebetween concentric conduits 58, 60, air box 52, and lower ducts 56. Asthe hot combustion gases rise in the heat exchanger, the walls thereofare heated, increasing the temperature of the surrounding air andthereby inducing a natural upward convection flow of room air into thebottom of the heater and out the top thereof through the cabinet 32.

The convergence of the intermediate wall sections of the heat exchanger50 compensates for the reduction in volume of the hot combustion gasesoccasioned by the transfer of heat to the vertically rising room air inthe heater, and the V-shaped baffle surface defined by the cooperatinggrooves 80 in the heat exchanger produces desirable flow of the hotgases for assuring efficient heat transfer before such gases dischargefrom the heater. The radiation shield 98 will be efiective to preventundesirable heating of the air box and mounting box rear wall byradiation from the heat exchanger.

It will be noted that during the natural convection flow of room airthrough the heater, some air will enter the bottom of the air jacketsurrounding the mounting box 30 and rise upwardly therein for dischargethrough the top cabinet piece 220. The air jacket will thereby preventoverheating of the building wall as well as the cabinet, and moreover,some of this air will flow in the annular space between outer conduit 60and tube 102 to minimize the heat transferred to the building wall inthis region. If desired, insulation may be placed in this annular spaceand also in the space surrounding tube 102 for the same purpose.

An important advantage of the heater of the invention is the heatingeifect realized by operation of the blower in housing 210. Operation ofthis blower may be controlled by temperature responsive means positionedwithin the heater itself so that in the event the temperature within theheater becomes sufficiently high, the blower will be auomatically turnedon and pull downwardly some of the air rising in the rear space formedbetween mounting box and the heat exchanger. This downwardly drawn airflows through the fittings 200, 216 and into the blower housing 210 tobe discharged by the blower through tangential outlet duct 214 forsubsequent generally horizontal flow through the grille in the frontcabinet piece 232 at a level adjacent the floor. Thus, heated air willbe discharged from the heater simultaneously from the top and bottomthereof for eflicient heating. As will be understood, the displacementof the blower may be varied in accordance with the desired operatingcharacteristics so that more or less air will be pulled downwardlythrough the heater. Additionally, other blowers may be similarlyarranged at other positions in the mounting box, such as in the lowerright corner thereof, for increasing the downwardly forced aircirculation in the heater.

The external combustion-supporting air flowing through outer duct 60 andair box 52 will not be undesirably preheated inasmuch as the distance ittravels in contact with the hot inner conduit 58 is not very great, andthe temperature of the air box will be kept relatively low by the shield98. However, a tubular insulating collar (not shown) may be fittedaround the inner conduit 58 for this purpose.

As previously noted, the burner 54 may be conveniently attached to andremoved from the heat exchanger, and access for adjustment of thefuel-air ratio will be offered simply by opening the cabinet front piece232.

It will thus be seen that the objects of this invention have been fullyand effectively accomplished. It will be realized, however, that theforegoing specific embodiment has been shown and described only for thepurpose of illustrating the principles of the invention and is subjectto extensive change without departure from such principles. Therefore,this invention includes all modifications encompassed within the spiritand scope of the appended claims.

We claim:

1. In a wall mounted space heater; a heating unit adapted to be mountedadjacent a wall, a cabinet adapted to cooperate with the wall forenclosing said heating unit, a mounting box adapted to be disposedintermediate said heating unit and the wall and define an air jacketdirectly with the wall and said cabinet, said cabinet having upper andlower openings for upward convection flow of room air in heat exchangerelationship with said heating unit, a separate wall member attached tolaterally spaced regions of said mounting box and on the same side ofsaid mounting box as said heating unit, said wall member being spacedfrom the portion of said mounting box between said regions so as to formtherewith a duct means having an upper inlet and a lower outlet, and ablower operatively secured to the lower end of said duct means forinducing a downward flow through said duct means of some of the airrising in said heater and discharging such air adjacent the floor of theroom.

2. The structure defined in claim 1 wherein the mounting box includesback and side walls, said back wall adapted to be disposed parallel tothe room wall, brackets on said back wall adapted to attach it to theroom wall; and wherein the cabinet includes means cooperating with saidbrackets for releasably retaining said cabinet in enclosing relationwith respect to said heating unit.

3. The structure defined in claim 2 wherein the means included by thecabinet includes a top wall having a depending flange, and said bracketshaving notches therein for engagement by said flange.

4. A combined combustion air inlet and exhaust gas outlet structureadapted to be attached to a wall mounted, hermetically sealed heaterhaving concentric conduits connected to a heat exchanger and extendingthrough the wall on which the heater is mounted: said structureincluding: a mounting plate adapted to be attached to the outside of thebuilding wall and having a central aperture therein defined by aninturned flange engageably secured to the outer concentric conduit; adish-shaped member arranged outwardly of said mounting plate and havinga convex central portion provided with an aperture at its apex, saidaperture being defined by an inturned flange engageably secured to saidinner conduit; means attached to the periphery of said dish-shapedmember and disposed parallel to said mounting plate to provide aperipheral inlet of substantially constant width for said outer concentric conduit; an apertured sleeve connecting said mounting plate tosaid last-named means, one end of said sleeve being secured to theinturned flange of said mounting plate; a generally dish-shaped cap forsaid inner concentric conduit spaced axially outwardly of said dishshaped member and connected thereto; and at least one batfie disposedintermediate said cap and said member and defining therewith generallyradial passageways of substantially uniform width communicating withsaid inner conduit.

5. The structure defined in claim 4 wherein the means attached to theperiphery of the dish-shaped member has an outturned flange defining acentral aperture concentric with and substantially equal in diameter tothe aperture in the mounting plate, and wherein the other end of theapertured sleeve is secured to said outturned flange.

References Cited in the file of this patent UNITED STATES PATENTS100,268 DeLandsee Mar. 1, 1870 687,668 Taylor Nov. 26, 1901 1,674,643Hartwig June 26, 1928 2,160,883 Lundstrum June 6, 1939 2,192,920 LinchMar. 12, 1940 2,241,025 Wedderspoon May 6, 1941 2,243,916 Mueller June3, 1941 2,632,435 Lundstrum Mar. 24, 1953 2,671,500 Jones Mar. 9, 19542,692,186 Reznor Mar. 9, 1954 2,755,794 Wendell July 24, 1956 2,764,972Ryder Oct. 2, 1956 2,818,059 Cayot Dec. 31, 1957 FOREIGN PATENTS 736,326Great Britain Sept. 7, 1955

